CA1120429A - Treatment of cation exchange membrane with monoamine its salt, or quaternary ammonium salt - Google Patents
Treatment of cation exchange membrane with monoamine its salt, or quaternary ammonium saltInfo
- Publication number
- CA1120429A CA1120429A CA000298200A CA298200A CA1120429A CA 1120429 A CA1120429 A CA 1120429A CA 000298200 A CA000298200 A CA 000298200A CA 298200 A CA298200 A CA 298200A CA 1120429 A CA1120429 A CA 1120429A
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- Prior art keywords
- membrane
- salt
- treatment
- treated
- cation exchange
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/20—Manufacture of shaped structures of ion-exchange resins
- C08J5/22—Films, membranes or diaphragms
- C08J5/2287—After-treatment
- C08J5/2293—After-treatment of fluorine-containing membranes
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
- C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
- C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for the electrolysis of alkali halide. Use is made of a cation exchange membrane having as its ion exchange radicals, sulfonic acid radicals. This membrane is treated with primary, secondary or tertiary monoamine or its salt or quater-nary ammonium salt and then heat-treated at a temperature higher than 100°C and lower than melting point of the reaction product and then subjected to drying, so as to improve the cation-selecting performance of the membrane and to increase its current efficiency.
A process for the electrolysis of alkali halide. Use is made of a cation exchange membrane having as its ion exchange radicals, sulfonic acid radicals. This membrane is treated with primary, secondary or tertiary monoamine or its salt or quater-nary ammonium salt and then heat-treated at a temperature higher than 100°C and lower than melting point of the reaction product and then subjected to drying, so as to improve the cation-selecting performance of the membrane and to increase its current efficiency.
Description
` .~.1.;~3~2~
This invention rela-tes to a process for the electro-lytic treatment of alkali halide, and more speciically, it relates -to the said kind of electxolytic process with use of a cation exchange membrane.
Cation exchange membranes find broad industrial usage in the process of electric dialysis, diffusion dialysis and the like, and as separating membranas in electro-reaction processes. Especially, in the latter, the membrane must represent an as low as possible electric resistance during the - electrolysis, a superior selective permeability to anions or cations which are specifically selected to pass therethrough, and physical and chemical stability during use. For u~e in the electrolytic treatment of alkali halide~ chemical stability of the membrane is especially desired.
For satisfying this characteristic, the membrane is desirably made of fluorocarbon resin material. It has been experienced, however, that the fluorocarbon resin base cation -~ exchange membrane works only inadequately in respect to chemical stability as well as selective permeability. Especially and generally speaking, when treating high concentration electrolytic solution, the performance of the membrane de-creases to a ~ubstantial degree.
It should be noted that the selection of the membrane material significantly depends upon the current efficiency in the electrolytic treatment of alkali halide solution. Therefore, in view of this fact, it has long been desired among those skilled in the art to provide a superior electrolytic membrane, having a better selective permeability for cations, and an as low as possible electric resistance.
' .
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~' .
1 SUMMARY OF T~IE INVENTION
It is, therefore, the main object oE the invention to provide a highly eficient process for the electroly-tic treat-ment of alkal.i halide solution by the use of an improved catior exchange membrane.
According to the present inven-tion, the cation ex-change membrane carrying, as its ion exchange radical, sulfonic acid radical, is trea-ted with any one of or any combination of salt(s) of primary, secondary or ter-tiary monoamines or alterna-tively with quaternary ammonium salt, to improve the ionic ~: selectability.
It is well acknowledged that the cation exchangemembrane carrying sulfonic acid radicals as its ion exchange radical has an appreciable affini-ty to water on accoun-t of the specifically selected active ions. In this case, when the mother resin material ha~ nct been suf~iciently cross-linkedj it will become swollen by co.ntact ~ith water or aqueous electrolytic solution. With a higher content of the sulfonic acid radicals than a predetermined value, it may be frequently experienced ~n that ionic selectivity lessens as the content of sulfonic acid --~ radicals increases. In order to avoid such disadvantageous phenomenon, the degree of possible swelling may be advantageous-ly lowered by applying further cross-linking treatment to the mother resin material to a proper degree. On -the other hand, however, there generally are difficulties in the machinability of the cross-linked resin. Although the ion exchange membrane must be as thin as possible in order to represent an as small as possible electric resistance, the cross-linked resin membrane is very difficult to produce with a prescribed thinness, 3~ particularly on account of the aforementioned mechanical
This invention rela-tes to a process for the electro-lytic treatment of alkali halide, and more speciically, it relates -to the said kind of electxolytic process with use of a cation exchange membrane.
Cation exchange membranes find broad industrial usage in the process of electric dialysis, diffusion dialysis and the like, and as separating membranas in electro-reaction processes. Especially, in the latter, the membrane must represent an as low as possible electric resistance during the - electrolysis, a superior selective permeability to anions or cations which are specifically selected to pass therethrough, and physical and chemical stability during use. For u~e in the electrolytic treatment of alkali halide~ chemical stability of the membrane is especially desired.
For satisfying this characteristic, the membrane is desirably made of fluorocarbon resin material. It has been experienced, however, that the fluorocarbon resin base cation -~ exchange membrane works only inadequately in respect to chemical stability as well as selective permeability. Especially and generally speaking, when treating high concentration electrolytic solution, the performance of the membrane de-creases to a ~ubstantial degree.
It should be noted that the selection of the membrane material significantly depends upon the current efficiency in the electrolytic treatment of alkali halide solution. Therefore, in view of this fact, it has long been desired among those skilled in the art to provide a superior electrolytic membrane, having a better selective permeability for cations, and an as low as possible electric resistance.
' .
`~ ~
~' .
1 SUMMARY OF T~IE INVENTION
It is, therefore, the main object oE the invention to provide a highly eficient process for the electroly-tic treat-ment of alkal.i halide solution by the use of an improved catior exchange membrane.
According to the present inven-tion, the cation ex-change membrane carrying, as its ion exchange radical, sulfonic acid radical, is trea-ted with any one of or any combination of salt(s) of primary, secondary or ter-tiary monoamines or alterna-tively with quaternary ammonium salt, to improve the ionic ~: selectability.
It is well acknowledged that the cation exchangemembrane carrying sulfonic acid radicals as its ion exchange radical has an appreciable affini-ty to water on accoun-t of the specifically selected active ions. In this case, when the mother resin material ha~ nct been suf~iciently cross-linkedj it will become swollen by co.ntact ~ith water or aqueous electrolytic solution. With a higher content of the sulfonic acid radicals than a predetermined value, it may be frequently experienced ~n that ionic selectivity lessens as the content of sulfonic acid --~ radicals increases. In order to avoid such disadvantageous phenomenon, the degree of possible swelling may be advantageous-ly lowered by applying further cross-linking treatment to the mother resin material to a proper degree. On -the other hand, however, there generally are difficulties in the machinability of the cross-linked resin. Although the ion exchange membrane must be as thin as possible in order to represent an as small as possible electric resistance, the cross-linked resin membrane is very difficult to produce with a prescribed thinness, 3~ particularly on account of the aforementioned mechanical
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1 difEiculties. :[n addition, it has been frequently experienced tha-t the mechanical strength of the cross-linked resin membrane becomes smaller upon contact with water or aqueous electrolytic solution.
Takiny the above facts into account, it is, therefore, highly preferable ~o provide ion exchange membranes with a suitable content of sulfonic acid radicals.
When considering the catiQn exchange membrane of fluorocarbon resin which is known as highly advantageous as an ion exchanger in the electrolytic treatment of alkali halide, if an exchanger is used containing a lower ratio of sulfonic acid radical-containing monomer relative to the fluorocarbon monomer,-the difficulty in the mechanical workability will be extreme on account of the high content of the fluorocarbon resin, and especially, in the case of the ion exchange membrane which requires an as small as possible electric resistance, the required thinness is extremely difficult to realiæe. If the amount of such monomer containing sulfonic acid radicals or those later transformable thereinto is increased beyond a pre 20 determined limit for avoiding the above defect, the degree of swelling as appearing upon contact with water or aqueous solution will be disadvantageously high and the current efficiency as appearing during electrolysis of alkali halide will thus be inferior It is our proposal for avoiding these conventional defects to treat such cation exchange membrane carrying a relatively high amount of sulfonic acid radicals, and indeed, with salt of primary, secondary or tertiary monoamine or with quaternary ammonium salt. By use of such a modified and improved cation exchange membranej the ionic selective permeability of ..~
,2~
1 the latter can be amaæinyly el~vated during the course of electro-lytic treatment of alkali halide solution.
~ s is commonly known/ when sulfonic acid radical or its me-tal ~alt is reacted with salt of primary J secondary or tertiary monoamine or with quaternary ammonium salt, a sulfonic acid-ammonium complex oE the ~ollowing form i9 provided:
o _o~ (~Rl R ~ R )~
O
where Rl, R2~ R3 or R4 stands for hydrogen or a radical : forming an ammonium bond.
Various prior proposals have been hitherto made to treat the cation exchange membran0 with amine. For example, a polyamine, preferably ethyl0n0 d.iamine has been proposed for the treatment of memhrane carrying radicals of -SO2X, X being C1 or F. This proposed process has as i~s object the provision of a . cross-linking reaction in the basic resin with the polyamine, ." wherein, however, the resultin~ bonding radical consists of sul-~p famide. The abo~e known process contributes to improve the lonic 2~ selectivity performance while disadvantageously increasing the eIectric resistance value of the membrane.
~: As another example it is known that sulfonic acid radical of the cation exchange membrane can be reacted with a primary, secondary or t~rtiary amine salt or with quaternary ammonium salt or the like, as is employed in the present invention and then, the reacted product can be m01ted. It should, however, be noted that this known process is d~rected to repair locally defective parts of the membrane by melting and that the so repaired membrane parts represent a lower ion exchange .
1 performance than the remaining unrepaired parts of the membrane.
It is stressed tha~ the improved membrane according to this inventionprepared by treatment with primary, secondary or tertiary amine salt or with quaternary ammonium salt can hold - its improved ionic selective performance for an extended period under the electrolytic reaction conditions while keeping the electric resistance value at a low level.
It is believed, as hereinbefore disclosed, that the improved membrane accordlng to this invention comprises sulfonic 1~ acid-ammonium complex salt. According to common knowlQdge, it could not be conceived that such a type of complex salt as above i.s stable for extended periods of time~ In fact, the ammonium xadical bonded with the sulfonic radical is almost all separated during the electrolytic operation period and replaced by the alkali metal ion~s). It is, therefore, surprising that the effect o~ amine or ammonium treatment can be maintained for a long time in the case of the present inv~ntion.
It has not yet been completely clar.ified as to why the ionic selective performance is highly superior with the improved ~ membrane according to the invention, but the following explana-tion discusses what is believed to be an important factor ~- relating to a new conception of the hydration mechanism~
Before an ion exchange membrane is suspended under te~sion in the electrolytic bath, it must be swollen to a certain degree for softening, and even with the membrane according to this invention, carrying the ammonium complex salt transformingly provided in the foregoing way and thermally after-treated in the manner to be set forth, it is necessary before suspension in the bath to initially swell it with water or other suitable solvent.
During the electrolytic process, the ammonium complex will be 2V~29 I transformed to sulfonic acid -Na which is after all hydrated per se. It may thus be observed that both the conventional and inventive membranes carry equally the sulfonic acid -Na type component and are, therefore, similar to each other in chemical structure. It may be -Eurther observed that the membranes carry-ing sulfonic acid -Na component have substantially similar hydra-ting power and, accordinglyj should swell to a similar degree.
In fact, ~owever, there is a substantial difference in the oper-ating performance between the membrane subjected to the improving ~ treatment according to this invention and the conventional one having been untreated in the above sense and such difference is due to the anion-passing performance of these two membranes.
More specifically, these ions pass ~hrough the swelling water component contained in the improved membrane, while, in the conventional membrane, these ions are unable to similar ~ y pass ~ through the swelling water contained in the conventional membrane `~ which is in effect a barrier to the ions.
` It can be assumed that due to the electrically negative ~` nature of the sulfonic acid radicals, the suIfonic acid radicals and the hydrating water associated with the sulfonic acid radi-: , .
cals are intimately attracted to each other, whereas all anions are repulsed by the sulfonic acid radicals and thus prevented from associating with the sulfonic acid radicals. Therefore, if the swelling water is composed exclusively of hydrating water components associated with the sulfonic acid salts, it will be very difficult for anions to penetrate or pass through the mem-brane. However, there are such aqueous components which are not in-Eluenced by the practically existing sulfonic acid radicals and the anions may-pass through the membrane substantially Ereely via such aqueous components in the membrane, It is, , ~ .
;
g therefore, conce:ivab.le that there ~a~ possibly be present a signi~icant quanti-ty of swelling water in the area of the membrane which is not affected by the presence of the practically included sulfonic radicals, if the membrane has not been subjected to the improv~ng treatment accord~ng to the invention.
As strong suppor-t ~or the ~bove s.upposition/ we have - found tha-t if the once amine-treated membrane is treated ~urther with a thermal tre~tment at a sufficIently h~,gh temperature to invite thermal contraction, -th~se areas in whichthe sulfonic acid rad~cals have no i.nfluence in the above sense are eliminated, The above disclosed explanation for the i,ncrease in the ~onic selecti,ve. permea~iI,i,k~v~ i~5 based onl~ on ~n ass,umption, The formati.~n of an ammoni.um complex may also provide a favourable ef~ect. Furth.er conceivable i5. the occurrence of a k~.nd oE rear ~, rangement of the sulfonic acid radlc~ls In the sens,e of s.tero;~so-'~ merism. ~fter all, ît should be noted that the membrane whiich has been sub~ected to the treatment with'primary, secondary~ or tert~ry monoamines or with the s.alts thereof or w.i,th.quarter-~; nary ammon~um sal~ and to a heat treatment, carries an ionIcally ~9 dissoc~atable complex provi:s:ionally formed, which dissoci:a-tes .into corresponding component i,ons:, and the thus: improved mem~rane facilitate~ a h~,ghly improYed current e~ficienc~ without inv;~ting .increasea flo~ resistance, w,hen the mem~rane is used for the electrolys.i:s of alkali halide~ wh;~.le the convention~l membrane' carries sulfam~de whi,ch.is di,ffi,cult to dI,ssoc~ate ,i~nto corresponding LOn components.
The am~ne usable in the present invention ,i~,s pre-ferab.ly a salt of primary, s,econdar~ or tertiary~ a~ine~ or quater-nary ammon;~um salt, having generally a form of the monoammoni:um ~ ~ .
i structure of (NRlR2R3~)X. In this general formula, Rl may preferably stand for alkyl, aryl or aralkyl or its halogen deri-vative. R2, R3 or R4 may stand for H or any one of those groups attributable to ~1 On the other hand, X stands for F, Cl, Br, I, OH or N03 or inorganic or organic acid radical preferably such as carboxylic acid radical as CH3COO.
With such structure as NH4X, that is, with the struc-ture (NRlR2R3R4)X wherein all the radicals Rl to R4 exist as H, no favorable results have been attained according to our ~ practical experiments.
When the hydrogen atoms of the alkyl or the like are replaced partially by certain hydrophilic radical such as -OH
or -COO~, with use of alcoholic amine or amino acid, favorable effects can not be provided.
The cation exchange radical which is to be subject to reaction with the monoamine or its salt according to this invention may be a sulfonic acid radical, as the fixed ion ~- exchange radical, having an ion exchange capacity of 0.2 2.0 meg/g dry resin. There is no specific limitation to the sulfonic acid~radical~ Therefore, not only ~503H, for example, of the H-type, but also radicals such as -S03Na and -S03K, for example, of the alkali metal salt type or the salt type may be used.
- For the 503H-(salt) type, primary~ secondary or tertiary amine or its salt or quaternary ammonium or its salt may be successfully utilized for the purpose of the in~ention.
In the salt type such as -S03Na or -S03K, however, use of primary or secondary amine or its salt may occasionally lead to unfavor-able results. It may be assumed that the reaction of ammonium salt can be executed to a satisfying degree wlth the H-type active radical while the reaction is executed only to an ' ~,~
2~3 1 insufficient degree in the case of the salt type active radical such as -SO3Na.
Sinca the monoamine salt usable in the invention is generally soluhle in water, it is reacted in its aqueous solution with the cation exchange ion in the membrane, the concentration of the solution being preferably from 0.01 to 5.0 mol/lit.
The membrane is dipped in the solution, or alterna-tively the latter may be coated on the former. Generally speak-ing the membrane in its entirety is brought into contact with the aqueous solution of monoamine salt. However, if desired, the solution can be brought into contact with one surface of the membrane, so as to intentionally localize the desired lmproving effect.
The range o temperature suitable for the dipping or coating operation is gene~ally and practically unlimited.
Preferably, the range will be from room temperature to the boil-ing point of the aqueous solution of monoamine salt.
The duration of the dipping or coating operation may differ with variation of the temperatures at which the operation is conducted. Preferably, the duration of the operation is shorter than a week. Frequently, however, it is in the order of 24 hours.
The membrane subjected to the dipping or coating operation is next treated thermally, as has been mentioned here-inbefore. The heat trea~ing temperature is generally higher than 100C, preferably higher than 140C~ The uppermost tem-perature may be selected to be a temperature slightly lower than the fusing temperature of the base resin material of the membrane.
On the other hand, the thermal treating period may ': .
:
~ ~ ' _g .A' '.~.
.~
1 extend genera:Lly from several m.inutes to 20 hours, depending upon the kind of the monoamine sa].t and the treating temperature.
In the presen-t invention, th.is heat treatment is requisite. If this heat treatment were to be omitted, the origin~
ally improved ionic selective permeability may be temporarily maintained but the effect will usually soon be lost within a relatively short period, with the selectivity thus becoming that:
of the untreated membrane.
The temperature of the heat treatment is an important factor for the purposes o~ the invention. I~ the tempexature is lower than 100C, the durability period of the improved effect will become unacceptably short. With increase of the heat treating temperature, the treating period is pre~erably extended~
: When the membrane is subjected to a complete heat treatment es-pecially at a temperature higher than 140C, it has been found experimentally that the effectiveness of the improved membrane is subjected to substantially no adverse aging effect, thus being the most preferably membrane condition from the view point of desired improveness.
On the other hand, if the membrane had been subjected to a heat treatment at a higher temperature than the fusing point o~ the base resin material of the membrane improved by the advance treatment with amine- or ammonium salt, the membrane may suffer from undue thermal distortion or have defective per-forations, but also may be undesirabl~ desulfonated or even cross-linked, thereby increasing disadvantageously the electric resistancé and inviting a substantial decrease in ion exchange performance. Although the fusing point of the membrane resin per se varies with the kind and nature of the amine or ammonium used in the advance treatment, the treating temperatures may vary from 140C to 230C, preferably from 150C to 200C.
~ -10-1 The cation exchange membrane improved by the amine salt treatment and the heat treatment has a desirably high level of cation exchange performance, as has been hereinbefore referred to. For use in the electrolytic treatment oE NaCl, the separat ing membrane may be pretreated in a boiling water bath for 30 minutes to an hour before the practical use of the membrane. In this way, the elec-tric resistance can be further decreased. It is also possible to pretreat the membrane in a bath of organic solvent or a mixture of the latter ~ith water~ A cation exchange membrane improved by any o the treatments disclosed herèinabove has highly superior ion exchange performance as well as a favor-able value of electrical resistance auring its service period t and thus, it can be used industrially in a very advantageous manner.
BRIEF DESCRIPTION OF THE DRA~ING
The accompanying sole drawing represents the cuxrent efficiency of an improved membrane to be described later in Example 14, relative to the degree of swellin~ as appearing after NaCl-electrolysis and in a 20%-NaOH solution developed during the course of the electrolysis. The membrane will be designated as N-llO membrane adapted for use in the electrolysis as to be executed in Example 14~ The broken line represents the relation between the degree of swelling and the current efficiency as appearing after the execution of N~Cl-electrol~sis, the membrane having been preparatorily treated with trime-thyl benzyl ammonium chloride as will be later set forth therein.
Detailed Description of Preferred Examples Example 1 A sheet of cation exchange membrane "NAFION 390"
~2V~
1 difEiculties. :[n addition, it has been frequently experienced tha-t the mechanical strength of the cross-linked resin membrane becomes smaller upon contact with water or aqueous electrolytic solution.
Takiny the above facts into account, it is, therefore, highly preferable ~o provide ion exchange membranes with a suitable content of sulfonic acid radicals.
When considering the catiQn exchange membrane of fluorocarbon resin which is known as highly advantageous as an ion exchanger in the electrolytic treatment of alkali halide, if an exchanger is used containing a lower ratio of sulfonic acid radical-containing monomer relative to the fluorocarbon monomer,-the difficulty in the mechanical workability will be extreme on account of the high content of the fluorocarbon resin, and especially, in the case of the ion exchange membrane which requires an as small as possible electric resistance, the required thinness is extremely difficult to realiæe. If the amount of such monomer containing sulfonic acid radicals or those later transformable thereinto is increased beyond a pre 20 determined limit for avoiding the above defect, the degree of swelling as appearing upon contact with water or aqueous solution will be disadvantageously high and the current efficiency as appearing during electrolysis of alkali halide will thus be inferior It is our proposal for avoiding these conventional defects to treat such cation exchange membrane carrying a relatively high amount of sulfonic acid radicals, and indeed, with salt of primary, secondary or tertiary monoamine or with quaternary ammonium salt. By use of such a modified and improved cation exchange membranej the ionic selective permeability of ..~
,2~
1 the latter can be amaæinyly el~vated during the course of electro-lytic treatment of alkali halide solution.
~ s is commonly known/ when sulfonic acid radical or its me-tal ~alt is reacted with salt of primary J secondary or tertiary monoamine or with quaternary ammonium salt, a sulfonic acid-ammonium complex oE the ~ollowing form i9 provided:
o _o~ (~Rl R ~ R )~
O
where Rl, R2~ R3 or R4 stands for hydrogen or a radical : forming an ammonium bond.
Various prior proposals have been hitherto made to treat the cation exchange membran0 with amine. For example, a polyamine, preferably ethyl0n0 d.iamine has been proposed for the treatment of memhrane carrying radicals of -SO2X, X being C1 or F. This proposed process has as i~s object the provision of a . cross-linking reaction in the basic resin with the polyamine, ." wherein, however, the resultin~ bonding radical consists of sul-~p famide. The abo~e known process contributes to improve the lonic 2~ selectivity performance while disadvantageously increasing the eIectric resistance value of the membrane.
~: As another example it is known that sulfonic acid radical of the cation exchange membrane can be reacted with a primary, secondary or t~rtiary amine salt or with quaternary ammonium salt or the like, as is employed in the present invention and then, the reacted product can be m01ted. It should, however, be noted that this known process is d~rected to repair locally defective parts of the membrane by melting and that the so repaired membrane parts represent a lower ion exchange .
1 performance than the remaining unrepaired parts of the membrane.
It is stressed tha~ the improved membrane according to this inventionprepared by treatment with primary, secondary or tertiary amine salt or with quaternary ammonium salt can hold - its improved ionic selective performance for an extended period under the electrolytic reaction conditions while keeping the electric resistance value at a low level.
It is believed, as hereinbefore disclosed, that the improved membrane accordlng to this invention comprises sulfonic 1~ acid-ammonium complex salt. According to common knowlQdge, it could not be conceived that such a type of complex salt as above i.s stable for extended periods of time~ In fact, the ammonium xadical bonded with the sulfonic radical is almost all separated during the electrolytic operation period and replaced by the alkali metal ion~s). It is, therefore, surprising that the effect o~ amine or ammonium treatment can be maintained for a long time in the case of the present inv~ntion.
It has not yet been completely clar.ified as to why the ionic selective performance is highly superior with the improved ~ membrane according to the invention, but the following explana-tion discusses what is believed to be an important factor ~- relating to a new conception of the hydration mechanism~
Before an ion exchange membrane is suspended under te~sion in the electrolytic bath, it must be swollen to a certain degree for softening, and even with the membrane according to this invention, carrying the ammonium complex salt transformingly provided in the foregoing way and thermally after-treated in the manner to be set forth, it is necessary before suspension in the bath to initially swell it with water or other suitable solvent.
During the electrolytic process, the ammonium complex will be 2V~29 I transformed to sulfonic acid -Na which is after all hydrated per se. It may thus be observed that both the conventional and inventive membranes carry equally the sulfonic acid -Na type component and are, therefore, similar to each other in chemical structure. It may be -Eurther observed that the membranes carry-ing sulfonic acid -Na component have substantially similar hydra-ting power and, accordinglyj should swell to a similar degree.
In fact, ~owever, there is a substantial difference in the oper-ating performance between the membrane subjected to the improving ~ treatment according to this invention and the conventional one having been untreated in the above sense and such difference is due to the anion-passing performance of these two membranes.
More specifically, these ions pass ~hrough the swelling water component contained in the improved membrane, while, in the conventional membrane, these ions are unable to similar ~ y pass ~ through the swelling water contained in the conventional membrane `~ which is in effect a barrier to the ions.
` It can be assumed that due to the electrically negative ~` nature of the sulfonic acid radicals, the suIfonic acid radicals and the hydrating water associated with the sulfonic acid radi-: , .
cals are intimately attracted to each other, whereas all anions are repulsed by the sulfonic acid radicals and thus prevented from associating with the sulfonic acid radicals. Therefore, if the swelling water is composed exclusively of hydrating water components associated with the sulfonic acid salts, it will be very difficult for anions to penetrate or pass through the mem-brane. However, there are such aqueous components which are not in-Eluenced by the practically existing sulfonic acid radicals and the anions may-pass through the membrane substantially Ereely via such aqueous components in the membrane, It is, , ~ .
;
g therefore, conce:ivab.le that there ~a~ possibly be present a signi~icant quanti-ty of swelling water in the area of the membrane which is not affected by the presence of the practically included sulfonic radicals, if the membrane has not been subjected to the improv~ng treatment accord~ng to the invention.
As strong suppor-t ~or the ~bove s.upposition/ we have - found tha-t if the once amine-treated membrane is treated ~urther with a thermal tre~tment at a sufficIently h~,gh temperature to invite thermal contraction, -th~se areas in whichthe sulfonic acid rad~cals have no i.nfluence in the above sense are eliminated, The above disclosed explanation for the i,ncrease in the ~onic selecti,ve. permea~iI,i,k~v~ i~5 based onl~ on ~n ass,umption, The formati.~n of an ammoni.um complex may also provide a favourable ef~ect. Furth.er conceivable i5. the occurrence of a k~.nd oE rear ~, rangement of the sulfonic acid radlc~ls In the sens,e of s.tero;~so-'~ merism. ~fter all, ît should be noted that the membrane whiich has been sub~ected to the treatment with'primary, secondary~ or tert~ry monoamines or with the s.alts thereof or w.i,th.quarter-~; nary ammon~um sal~ and to a heat treatment, carries an ionIcally ~9 dissoc~atable complex provi:s:ionally formed, which dissoci:a-tes .into corresponding component i,ons:, and the thus: improved mem~rane facilitate~ a h~,ghly improYed current e~ficienc~ without inv;~ting .increasea flo~ resistance, w,hen the mem~rane is used for the electrolys.i:s of alkali halide~ wh;~.le the convention~l membrane' carries sulfam~de whi,ch.is di,ffi,cult to dI,ssoc~ate ,i~nto corresponding LOn components.
The am~ne usable in the present invention ,i~,s pre-ferab.ly a salt of primary, s,econdar~ or tertiary~ a~ine~ or quater-nary ammon;~um salt, having generally a form of the monoammoni:um ~ ~ .
i structure of (NRlR2R3~)X. In this general formula, Rl may preferably stand for alkyl, aryl or aralkyl or its halogen deri-vative. R2, R3 or R4 may stand for H or any one of those groups attributable to ~1 On the other hand, X stands for F, Cl, Br, I, OH or N03 or inorganic or organic acid radical preferably such as carboxylic acid radical as CH3COO.
With such structure as NH4X, that is, with the struc-ture (NRlR2R3R4)X wherein all the radicals Rl to R4 exist as H, no favorable results have been attained according to our ~ practical experiments.
When the hydrogen atoms of the alkyl or the like are replaced partially by certain hydrophilic radical such as -OH
or -COO~, with use of alcoholic amine or amino acid, favorable effects can not be provided.
The cation exchange radical which is to be subject to reaction with the monoamine or its salt according to this invention may be a sulfonic acid radical, as the fixed ion ~- exchange radical, having an ion exchange capacity of 0.2 2.0 meg/g dry resin. There is no specific limitation to the sulfonic acid~radical~ Therefore, not only ~503H, for example, of the H-type, but also radicals such as -S03Na and -S03K, for example, of the alkali metal salt type or the salt type may be used.
- For the 503H-(salt) type, primary~ secondary or tertiary amine or its salt or quaternary ammonium or its salt may be successfully utilized for the purpose of the in~ention.
In the salt type such as -S03Na or -S03K, however, use of primary or secondary amine or its salt may occasionally lead to unfavor-able results. It may be assumed that the reaction of ammonium salt can be executed to a satisfying degree wlth the H-type active radical while the reaction is executed only to an ' ~,~
2~3 1 insufficient degree in the case of the salt type active radical such as -SO3Na.
Sinca the monoamine salt usable in the invention is generally soluhle in water, it is reacted in its aqueous solution with the cation exchange ion in the membrane, the concentration of the solution being preferably from 0.01 to 5.0 mol/lit.
The membrane is dipped in the solution, or alterna-tively the latter may be coated on the former. Generally speak-ing the membrane in its entirety is brought into contact with the aqueous solution of monoamine salt. However, if desired, the solution can be brought into contact with one surface of the membrane, so as to intentionally localize the desired lmproving effect.
The range o temperature suitable for the dipping or coating operation is gene~ally and practically unlimited.
Preferably, the range will be from room temperature to the boil-ing point of the aqueous solution of monoamine salt.
The duration of the dipping or coating operation may differ with variation of the temperatures at which the operation is conducted. Preferably, the duration of the operation is shorter than a week. Frequently, however, it is in the order of 24 hours.
The membrane subjected to the dipping or coating operation is next treated thermally, as has been mentioned here-inbefore. The heat trea~ing temperature is generally higher than 100C, preferably higher than 140C~ The uppermost tem-perature may be selected to be a temperature slightly lower than the fusing temperature of the base resin material of the membrane.
On the other hand, the thermal treating period may ': .
:
~ ~ ' _g .A' '.~.
.~
1 extend genera:Lly from several m.inutes to 20 hours, depending upon the kind of the monoamine sa].t and the treating temperature.
In the presen-t invention, th.is heat treatment is requisite. If this heat treatment were to be omitted, the origin~
ally improved ionic selective permeability may be temporarily maintained but the effect will usually soon be lost within a relatively short period, with the selectivity thus becoming that:
of the untreated membrane.
The temperature of the heat treatment is an important factor for the purposes o~ the invention. I~ the tempexature is lower than 100C, the durability period of the improved effect will become unacceptably short. With increase of the heat treating temperature, the treating period is pre~erably extended~
: When the membrane is subjected to a complete heat treatment es-pecially at a temperature higher than 140C, it has been found experimentally that the effectiveness of the improved membrane is subjected to substantially no adverse aging effect, thus being the most preferably membrane condition from the view point of desired improveness.
On the other hand, if the membrane had been subjected to a heat treatment at a higher temperature than the fusing point o~ the base resin material of the membrane improved by the advance treatment with amine- or ammonium salt, the membrane may suffer from undue thermal distortion or have defective per-forations, but also may be undesirabl~ desulfonated or even cross-linked, thereby increasing disadvantageously the electric resistancé and inviting a substantial decrease in ion exchange performance. Although the fusing point of the membrane resin per se varies with the kind and nature of the amine or ammonium used in the advance treatment, the treating temperatures may vary from 140C to 230C, preferably from 150C to 200C.
~ -10-1 The cation exchange membrane improved by the amine salt treatment and the heat treatment has a desirably high level of cation exchange performance, as has been hereinbefore referred to. For use in the electrolytic treatment oE NaCl, the separat ing membrane may be pretreated in a boiling water bath for 30 minutes to an hour before the practical use of the membrane. In this way, the elec-tric resistance can be further decreased. It is also possible to pretreat the membrane in a bath of organic solvent or a mixture of the latter ~ith water~ A cation exchange membrane improved by any o the treatments disclosed herèinabove has highly superior ion exchange performance as well as a favor-able value of electrical resistance auring its service period t and thus, it can be used industrially in a very advantageous manner.
BRIEF DESCRIPTION OF THE DRA~ING
The accompanying sole drawing represents the cuxrent efficiency of an improved membrane to be described later in Example 14, relative to the degree of swellin~ as appearing after NaCl-electrolysis and in a 20%-NaOH solution developed during the course of the electrolysis. The membrane will be designated as N-llO membrane adapted for use in the electrolysis as to be executed in Example 14~ The broken line represents the relation between the degree of swelling and the current efficiency as appearing after the execution of N~Cl-electrol~sis, the membrane having been preparatorily treated with trime-thyl benzyl ammonium chloride as will be later set forth therein.
Detailed Description of Preferred Examples Example 1 A sheet of cation exchange membrane "NAFION 390"
3~ procured from E, Il DuPont, and of the sulfonic acid active .
~,~
.
: .
~.2~
f luorore5in type, whlch is composecl oE two membrane elements "EW 1100" and "EW 1500", was dipped in an aqueous solution con~
taininy trimethylamine hydrochloride in the ratio of 1 mol/lit~
for 17 hours. Then, the thus treated membrane was subjected to a heat treatment in an oven at 170C for 5 hours. The membrane was dipped in a boiling water bath for 30 minutes and then brought into service for the electrolysis of NaCl as the cation exchange membrane. The electrolysis was executed under the conditions as shown in the following Table 1. During electro-1~ lysis, the composite membrane was suspended in the electrolyticbath in such a state that the E~ 1500 was faced towards the cathode. The membrane positioning mode will be same as before in the following several Examples.
2~
, . .
~ -12-Cathode stainless steel Anode titanium~ruthenium oxide In-terelectrode Distance 5 mm Brine 26%-NaCl aqueous solution Rate of Decomposition about 10~
Bath Temperature 76 - 80 C
Current Density 20 A/dm3 The resulting electrolytic da-ta were as follows:
Concentration of NaOH-solution appearing at the cathodic chamber....~ ...22%;
Bath voltage..,..,.~...,.~...,3,4 volts which i5 lower than the initial operat:ing volt-age.
Current efficiency.. ,....... ,,~3%
When compared with the elec-trolytic results under util-ization of the same memkrane "NAFION 390" which had been pretreat-ed in a boiling water bath for 30 minutes/ the following results 0 ~ere obtained~
Concentration of NaOH-solution appearing at the cathodic chamber,.,.,...,,,.... 2a~;
Bath voltage~.. ,.. O.... ~.. ,.............. ~.~.~ t 3.2 volts;
Current efficiency...~ .. 75%;
It was found that the improved membrane used in the above Example 1 represented no reduction in the current efficiency even upon a continued electrolytic service for a~out three months, Thus, it was observed that the membrane improved as suggested in the present invention shows a superior ionic selective performance even upon an extended period of electrolytic service.
~: ~r V~
1 Example 2 The same NAFION 390-membrane as was used in the fore-going Example 1 was dipped in an aqueous solution containing 0.17 mol of tributylamine hydrochloride a~ 60C for 4 hours.
Then, the surfaces of the membrane ~ere wiped~ to remove excess liquid, with a filter paper, whereupon the membrane was subjected to a heat treatment at 160C Eor three hours and then dipped in a boiling water bath for 30 minutes. Then, the membrane was used for the treatment of NaCl-aqueous solution, as in the similar way lO in the foregoing Example 1.
Current density: 20 amperes/dm2 ~ Bath temperature: 72 C
`~ Concentration of caustic soda solution at cathodic chamber: 22,4%
Current e~ficiency: 94.4%
Bath voltage; 3.42 volts Examples 3 - 5 E. I. DuPont' 5 ca-tion exchange mem~rane, "N~FION 315", carrying as its active radicals~ sul.fonic acid radicals, ~as prer 2~ paxed. This was of the -SO3H-type, As the monoamine salt, iso-propylamine hydrochloride; dimethylamine hydrochloride and tetra-methylammonium chloride were successively us~d for the similar membranes, These membranes were used in each case, as the sep- -arator in the electrolysis of NaCl. The electrolytic conditions were same as those used in the foregoing Example 1, The results are shcwn in the following Table 2.
i~ concentration of Example monoamine salt current caustic sod efficiency solution , 3 isoproplyamine hydrochloride 91.4% 23.4
~,~
.
: .
~.2~
f luorore5in type, whlch is composecl oE two membrane elements "EW 1100" and "EW 1500", was dipped in an aqueous solution con~
taininy trimethylamine hydrochloride in the ratio of 1 mol/lit~
for 17 hours. Then, the thus treated membrane was subjected to a heat treatment in an oven at 170C for 5 hours. The membrane was dipped in a boiling water bath for 30 minutes and then brought into service for the electrolysis of NaCl as the cation exchange membrane. The electrolysis was executed under the conditions as shown in the following Table 1. During electro-1~ lysis, the composite membrane was suspended in the electrolyticbath in such a state that the E~ 1500 was faced towards the cathode. The membrane positioning mode will be same as before in the following several Examples.
2~
, . .
~ -12-Cathode stainless steel Anode titanium~ruthenium oxide In-terelectrode Distance 5 mm Brine 26%-NaCl aqueous solution Rate of Decomposition about 10~
Bath Temperature 76 - 80 C
Current Density 20 A/dm3 The resulting electrolytic da-ta were as follows:
Concentration of NaOH-solution appearing at the cathodic chamber....~ ...22%;
Bath voltage..,..,.~...,.~...,3,4 volts which i5 lower than the initial operat:ing volt-age.
Current efficiency.. ,....... ,,~3%
When compared with the elec-trolytic results under util-ization of the same memkrane "NAFION 390" which had been pretreat-ed in a boiling water bath for 30 minutes/ the following results 0 ~ere obtained~
Concentration of NaOH-solution appearing at the cathodic chamber,.,.,...,,,.... 2a~;
Bath voltage~.. ,.. O.... ~.. ,.............. ~.~.~ t 3.2 volts;
Current efficiency...~ .. 75%;
It was found that the improved membrane used in the above Example 1 represented no reduction in the current efficiency even upon a continued electrolytic service for a~out three months, Thus, it was observed that the membrane improved as suggested in the present invention shows a superior ionic selective performance even upon an extended period of electrolytic service.
~: ~r V~
1 Example 2 The same NAFION 390-membrane as was used in the fore-going Example 1 was dipped in an aqueous solution containing 0.17 mol of tributylamine hydrochloride a~ 60C for 4 hours.
Then, the surfaces of the membrane ~ere wiped~ to remove excess liquid, with a filter paper, whereupon the membrane was subjected to a heat treatment at 160C Eor three hours and then dipped in a boiling water bath for 30 minutes. Then, the membrane was used for the treatment of NaCl-aqueous solution, as in the similar way lO in the foregoing Example 1.
Current density: 20 amperes/dm2 ~ Bath temperature: 72 C
`~ Concentration of caustic soda solution at cathodic chamber: 22,4%
Current e~ficiency: 94.4%
Bath voltage; 3.42 volts Examples 3 - 5 E. I. DuPont' 5 ca-tion exchange mem~rane, "N~FION 315", carrying as its active radicals~ sul.fonic acid radicals, ~as prer 2~ paxed. This was of the -SO3H-type, As the monoamine salt, iso-propylamine hydrochloride; dimethylamine hydrochloride and tetra-methylammonium chloride were successively us~d for the similar membranes, These membranes were used in each case, as the sep- -arator in the electrolysis of NaCl. The electrolytic conditions were same as those used in the foregoing Example 1, The results are shcwn in the following Table 2.
i~ concentration of Example monoamine salt current caustic sod efficiency solution , 3 isoproplyamine hydrochloride 91.4% 23.4
4 dimethylamine hydrochloride 92.2% 21.1%
. 5 tetramethylammonium chloride 92.4% 20.8%
. .~,.-1 As a comparative Example 2, "NAFION 315"-memhrane with-out having been subjected to the monoamine salt treatmentr but dipped in a boiling water bath for 30 minutes was then used for ~he electrolytic treatmen~ of NaCl under the same operating con-ditions as in the foregoing Example 1. The electrolytic results were:
Concentration of NaOH~solution at cathodic chamber....... ,,.... ,... ~.,.. ,~. 21%;
Current ef~iciency........ ~..... ,.,,~,. 76~;
Thus, it was found that the mem~rane improved by the present in-vention represents a high and superior cation selecting perform-ance.
Example 6 The foregoing "N~315"-membrane was replaced hy such one, as of "-503Na"-type and the electrolysis was execuked with iso-propylamine hydrochloride under the similar operating conditions as was referred ~o in Example 3. The membrane was used as the ;~ separating wall mem~er. The results ~ere as follows:
Concentration of NaOH;solution at 2~ cathodic cham~er......... ~...... ~....... ,.,, 22.6%;
Current eficiency....... ,........... ,.. ..,, 85~.
From'the a~ove~ it can be observed that in this case~
the cation selecting performance was improved in a still better way than the case where the original "N-315"-membrane has been utilized. The degree o~ the improvement was better in khe present case, using the membrane of the -S03H-type was used.
Examples 7 - ~
The mem~rane of "N-315"-memhrane of the ~S03H type/ was dipped in an aqueous solution of trimethylamine hydrochloride, 0.3 mol~lit., at room temperature for 24 hours. Similar membranes ~15-,.~5~
were procured and prepared in the similar way and subjected each to a hea-t treatment at 160C; 180C and 225C, for two hours, respectively. Then, these membraneS were dipped in each case in a boiling water bath for 30 m.inutes and then brought into service for the electrolysis of NaCl and as the cation exchange membrane.
The results are shown in Table 3.
~ he electrolytic conditions were same as those used in the foregoing Example 1.
As comparative Example 3, the membrane was dipped only in an aqueous solution containing trimethylamine hydrochloride, 0.3 mol~lit., a~ .~oom temperature for 24 hours without execution of the heat treabment, ~ut further subjected to a dipping treat-ment in a boiling water bath for 30 minutes, The electrolytic results are shown stmultaneously in the same Table 3, Heat Treating Current Concentration of Example Temperature C Effi ~ caustic soda solution 7 160 91.6 2~,8%
. 8 180 ~2.0 22%
9 ~25 ~1.8 22%
Comparative ~
Example 3 , 82 21%
It can be well ackno~ledged for the purpose of the inventîon that the heat treatment o the membrane .i5 requisite after the execution of the amine salt treatment and for the ' ' .
,.. . .
1 improv~men-t oe the cati,on-selec-tion performance o~ the membxane.
_ample 10 NAFION 390 - membrane was fixed positioned on one end of an open-ended cylinder and a pool of same aqueous tximethyla-mlne hydrochlor~de solu-t~on as was used in the foregoing Example 1 was kept in the cyl~ndrical vessel or frame in contact with one surface of the membrane said surface being composed of the "EW
1500" - membrane element~ The contacting temperature was room temperature and the contacting period was four hours. The amine salt treatment was executed in this way.
The mem~rane was further treated thermally at 160C
for 3 hours and then, dipped in a boiling water bath for 30 minutes;. ~ith the 'created surface of the membrane directed to-wards the cathode, the membxane was then used in the e]ectrolyti~
txeatment ~f an aqueous NaCl-soluti~on under sim~lar operat~ng cond~tions ~s~,n the ~orego~ng Example lo The xesult~ ~ere:
Concentr~iQn of caus,t~c soda solut~on.,.q..20.3%;
Current eff~ci,ency..... r ~ 9 ~ t ~ 92~ 4~; -Bath voltage,.~. t 0.,.. ...........3~22 volts at 74Ct 20 EXamples 11 -- 12 ' Cation exchange membranes of "N ~ llQ" ~03H-t~pe2, carr~i,ng pendant type sulfon~c acid radi:cals and procured from E.I. DuPont, were d~pped in respective aque~us~'s:olut~an~r'con-taini,ng; tri:methylamine hydrochloride; and i,s~opxop~lam~ne hydrochloride, a . 5 mol~lit., respectively, and ~n the s;imilar ' comparati,ve Examples 4 - 6, N,N-dimethylglyc~ne hydrochlori,de;
triethanolamine hydrochIoride and ammon~,um chloride, ~5 mol/l~t., respectively, at 100C for an hour, and were each subjected to 'a heat treatment at 160C for three hours, respectively. Further, as comparative Examples 7 - 8, the membranes were dipped in an ~ .
. . .
L~L 29 1 aqueous solution, contaillin(3 20 wt.~ o~ trimethylamine and secon-dary butylamine, respec~ively, at 80C for an hour, and at 160C
for three hours, respectively.
These membranes were dipped in a boiliny water bath for an hour and the resulted aqueous sweLling degree was measured in each case. In addition, these membranes were used separa-tely for the electrolytic treatment of a NaCl-aqueous solution in each case.
The resulted experimental data are shown in the following Table 4 wherein Comparative Example 9 represents the results by use of the original "N-llO"-membrane.
Table 4 Degree of Current Swelling, Effici-Example Kind of am~ne wk~% ~ 1*,%
11 trimethylamine hydrochloride 17 78 20.3 12 isopropylamine hydrochloride 17 76.4 19.7 4 N,N dimethyl~lysihe 25 58.2 20.6 hydrochloride i .
tr-i~-thanolamine 29 56.7 21.3 - hydrochloride ~0 6 ammonium chloride 25 59.4 l8.6 7 trimethylamine 17 60.2 19.9 8 sec. butylamine -- 61.9 21~2 9 --- 26 57 20.1 Remarks: l* . . . concentration of caustic soda solution Example 13 A cation exchange membrane "Nafion N-llO", of the -SO3H-type carrying pendant type sulfonic acid radicals and pro-cured from E.I. DuPont, was dipped in an aqueous solution con-taining trimethylbenzyl ammonium chloride, 1 mol/lit., and under refluxed conditions for about two hours ~ _~_ . .
2~
1 This membrane was fur-ther subjected to a heat treat-ment at 160C for Eive hours. According to infra red spectrum sur~ace observation, respective absorptions were seen at 1050 and 970 cm l, respectively, by virtue oE the presence of SO3 .
These positions and strengths at 1050 and 970 cm lr respectively, were just same wlth those obtainable with the original correspond-ing membrane which had not been treated with amine salt.
Then, these me~branes were dipped in a boiling water bath each for 30 minutes and used separately for the electrolytic treatment of NaCl under the same conditions as was disclosed in the ~oregoing Example l, and as the cation exchange membrane in each case.
Although the initial bath voltage showed a rèl~tively high value, however, it dr~pped to 3~2 volts after lapse~ of one day. The current efficiency amounted to 67% for the productlon of 20.3~ of NaOH.
An untreated membrane t'N-110" was dipped in a boi.ling water bath for 30 minutes and then used as the cation exchange membrane for tha same purpose under the same operating conditions to treat NaCl as ~efore, the current efficiency amounted to 58%
for producing 21.4~ - NaOH. This me~ns a considerably lower value. The bath voltage was 3 0 volts. From these results, the superior cation permeability of the amine salt-trea~ed membranes ; may be clearly seen.
After lapse of 48 hours of the electrolytic -treatment of the aqueous Na~ solution with use of the amine salt-treated membrane, the latter was washed with water and then dried up.
When observing the infra red spectrums, it was found that other-wise appearing absorptions caused by the presence of benzyl ra-.~ 30 dical and at 700 and 750 cm l, respectively, had complètely .; .
,': .,~ /1 ,. ,~, ,~_ 1 disappeared, showing those c~btail-able with untreated N-llO mem-branes.
It may be well suppoxed that during two day-electrolytic treatment period of NaCl that the arnine salt has been completely separated.
When observed with ultra violet spectrum, it was ob-served that the trimet~ylammonium chloride aqueous solution shown max ~ value at 260 ~.
When said N-llO membrane was dipped in a trimethylbenzyl ammonium chloride aqueous solution at 80C for about an hour and the amine salt aqueous solution was analyzed under UV-spectrum before and after the treatment, i-t was found that the a~line salt was consumed during the treatment in the specific ~uantlty of 0.~9 x 10 3 mol/g dry resin, and that the amine salt had reacted substantially in one-to-one reacting ratio with the ion-exchangeable radicals present in and on the membrane substxate.
~; From the foregoing, it may be well supposed that by the foregoing aMine salt treatment, an ion complex of (S03 )(N
is once formed which can be, however, easily separated off in the course of the electrolytic treatment of NaCl, Example 14 ~ hen the "NAFION N-llO"-rnembrane treated with trimethyl-benzyl ammonium chloride which was used in the foregoing Example 13, and then heat treated, is dipped in a boiling water bath for 30 minutes, it represents an aqueous swelling rate of about 11%. When this membrane is used for the electrolysis of NaCl under the operating conditions as set forth hereinbefore in Table 1 and at a 20% concentration of the NaOH pres~nt in the cathodic chambers the results will be:
Current efficiency .~ 69~;
Bath voltage....,....,. .~,~,..~..., ,..~.,.3.15 volts;
. ' ,.
a~
~z~
1 After lapse of three days, the membrane is taken out and the rate oE swelling thereo~ in a 20%-NaOH aqueous solution, amounts to abou-~ 14%
On the other hand, when a sheet of membrane "NAFION N-110"
is dipped in an aqueous NaOH-solution at 80C for an hour, the rate of swelling decreases with increased concentra-tion o~ the NaOH-solution. When these membranes are used for the electrolysis of NaCl under the operating conditions as set forth in the fore-going Table 1 and at a concentration of 20% of NaOH-solution present in the cathodic chamber, the current efficiency will vary with increase of the degree of swelling~ With the lower rate of swelling of the membrane treated beforehand with higher concen-tration of NaOH-solution, the current efficiency and the bath voltage will be higher.
After lapse of three days of electrol~tic tre~tment the membrane is taken out and subjected again to measurement of , the swelling degree in a 20%-NaOH-~queous solution, The swelling degree is found to have varied, as shown on the attached drawing.
When the membrane is treated with an aqueous solution O~ trimethyl benzyl ammonium chloride and then used for the desired electrolysis, the degree Q~ swelling being 14%, the treated membrane shows a current e~iciency of 69% and ~ bath voltage of 3.15 volts, while the corresponding caustic soda-treated membrane showing the similar`degree of swelling: 14%, shows à
current efficiency of 61%, respectively. Therefore, it will be seen that with same degree of swelling, the amine salt-treated membrane shows a rather favourahle effect. In this case, the quantity of ion exchange radicals: (-SO3Na)j can be deemed as subject to no change. When the respective concentration of Ma and OH present in the membrane substrate are expressed by CNa and COH , the ratio of COH / CNa will be same in the .:~ ` ' '` .
~ `
both. Now assuming the respective moving velocities of OH ~ions and Na ~ions are expres~ed by U~ and U~a , then the ratio betweerl the both will be:
, Ur OH / Na In that the product of the concentration of an ion in the membrane and the velocity of the ion in the membrane represents the current expended in passage of the ion through the membrane, current ef-ficienc~, Ceff~ representing the percentage of current supplied which contributes to the formation of NaOH may be defined as follows:
C = 100 x (CNa Na ; e~f - .
UNa ) ~ ~COH U~H
From the deining equations of Ur and Ce~ the following rela-tionship may be derived:
[ 100 1 r (COH / CN ~ , Ceff .-When Ur is calculated from this formula~ its valuefor the membranes treated with trime-th~lbenzyl ammonium chl~ride will be lower by about 30 in comparison with that of the membranes which have not been subjected to such salt treatment, The above difference may be attributed to the ~act that the membranes subjected to amine salt treatment as suggested herein represent generally a substantially improved current efficienc~ and with least possible increase of the bath ~ltage.
3~
.~
:', .
~.
. 5 tetramethylammonium chloride 92.4% 20.8%
. .~,.-1 As a comparative Example 2, "NAFION 315"-memhrane with-out having been subjected to the monoamine salt treatmentr but dipped in a boiling water bath for 30 minutes was then used for ~he electrolytic treatmen~ of NaCl under the same operating con-ditions as in the foregoing Example 1. The electrolytic results were:
Concentration of NaOH~solution at cathodic chamber....... ,,.... ,... ~.,.. ,~. 21%;
Current ef~iciency........ ~..... ,.,,~,. 76~;
Thus, it was found that the mem~rane improved by the present in-vention represents a high and superior cation selecting perform-ance.
Example 6 The foregoing "N~315"-membrane was replaced hy such one, as of "-503Na"-type and the electrolysis was execuked with iso-propylamine hydrochloride under the similar operating conditions as was referred ~o in Example 3. The membrane was used as the ;~ separating wall mem~er. The results ~ere as follows:
Concentration of NaOH;solution at 2~ cathodic cham~er......... ~...... ~....... ,.,, 22.6%;
Current eficiency....... ,........... ,.. ..,, 85~.
From'the a~ove~ it can be observed that in this case~
the cation selecting performance was improved in a still better way than the case where the original "N-315"-membrane has been utilized. The degree o~ the improvement was better in khe present case, using the membrane of the -S03H-type was used.
Examples 7 - ~
The mem~rane of "N-315"-memhrane of the ~S03H type/ was dipped in an aqueous solution of trimethylamine hydrochloride, 0.3 mol~lit., at room temperature for 24 hours. Similar membranes ~15-,.~5~
were procured and prepared in the similar way and subjected each to a hea-t treatment at 160C; 180C and 225C, for two hours, respectively. Then, these membraneS were dipped in each case in a boiling water bath for 30 m.inutes and then brought into service for the electrolysis of NaCl and as the cation exchange membrane.
The results are shown in Table 3.
~ he electrolytic conditions were same as those used in the foregoing Example 1.
As comparative Example 3, the membrane was dipped only in an aqueous solution containing trimethylamine hydrochloride, 0.3 mol~lit., a~ .~oom temperature for 24 hours without execution of the heat treabment, ~ut further subjected to a dipping treat-ment in a boiling water bath for 30 minutes, The electrolytic results are shown stmultaneously in the same Table 3, Heat Treating Current Concentration of Example Temperature C Effi ~ caustic soda solution 7 160 91.6 2~,8%
. 8 180 ~2.0 22%
9 ~25 ~1.8 22%
Comparative ~
Example 3 , 82 21%
It can be well ackno~ledged for the purpose of the inventîon that the heat treatment o the membrane .i5 requisite after the execution of the amine salt treatment and for the ' ' .
,.. . .
1 improv~men-t oe the cati,on-selec-tion performance o~ the membxane.
_ample 10 NAFION 390 - membrane was fixed positioned on one end of an open-ended cylinder and a pool of same aqueous tximethyla-mlne hydrochlor~de solu-t~on as was used in the foregoing Example 1 was kept in the cyl~ndrical vessel or frame in contact with one surface of the membrane said surface being composed of the "EW
1500" - membrane element~ The contacting temperature was room temperature and the contacting period was four hours. The amine salt treatment was executed in this way.
The mem~rane was further treated thermally at 160C
for 3 hours and then, dipped in a boiling water bath for 30 minutes;. ~ith the 'created surface of the membrane directed to-wards the cathode, the membxane was then used in the e]ectrolyti~
txeatment ~f an aqueous NaCl-soluti~on under sim~lar operat~ng cond~tions ~s~,n the ~orego~ng Example lo The xesult~ ~ere:
Concentr~iQn of caus,t~c soda solut~on.,.q..20.3%;
Current eff~ci,ency..... r ~ 9 ~ t ~ 92~ 4~; -Bath voltage,.~. t 0.,.. ...........3~22 volts at 74Ct 20 EXamples 11 -- 12 ' Cation exchange membranes of "N ~ llQ" ~03H-t~pe2, carr~i,ng pendant type sulfon~c acid radi:cals and procured from E.I. DuPont, were d~pped in respective aque~us~'s:olut~an~r'con-taini,ng; tri:methylamine hydrochloride; and i,s~opxop~lam~ne hydrochloride, a . 5 mol~lit., respectively, and ~n the s;imilar ' comparati,ve Examples 4 - 6, N,N-dimethylglyc~ne hydrochlori,de;
triethanolamine hydrochIoride and ammon~,um chloride, ~5 mol/l~t., respectively, at 100C for an hour, and were each subjected to 'a heat treatment at 160C for three hours, respectively. Further, as comparative Examples 7 - 8, the membranes were dipped in an ~ .
. . .
L~L 29 1 aqueous solution, contaillin(3 20 wt.~ o~ trimethylamine and secon-dary butylamine, respec~ively, at 80C for an hour, and at 160C
for three hours, respectively.
These membranes were dipped in a boiliny water bath for an hour and the resulted aqueous sweLling degree was measured in each case. In addition, these membranes were used separa-tely for the electrolytic treatment of a NaCl-aqueous solution in each case.
The resulted experimental data are shown in the following Table 4 wherein Comparative Example 9 represents the results by use of the original "N-llO"-membrane.
Table 4 Degree of Current Swelling, Effici-Example Kind of am~ne wk~% ~ 1*,%
11 trimethylamine hydrochloride 17 78 20.3 12 isopropylamine hydrochloride 17 76.4 19.7 4 N,N dimethyl~lysihe 25 58.2 20.6 hydrochloride i .
tr-i~-thanolamine 29 56.7 21.3 - hydrochloride ~0 6 ammonium chloride 25 59.4 l8.6 7 trimethylamine 17 60.2 19.9 8 sec. butylamine -- 61.9 21~2 9 --- 26 57 20.1 Remarks: l* . . . concentration of caustic soda solution Example 13 A cation exchange membrane "Nafion N-llO", of the -SO3H-type carrying pendant type sulfonic acid radicals and pro-cured from E.I. DuPont, was dipped in an aqueous solution con-taining trimethylbenzyl ammonium chloride, 1 mol/lit., and under refluxed conditions for about two hours ~ _~_ . .
2~
1 This membrane was fur-ther subjected to a heat treat-ment at 160C for Eive hours. According to infra red spectrum sur~ace observation, respective absorptions were seen at 1050 and 970 cm l, respectively, by virtue oE the presence of SO3 .
These positions and strengths at 1050 and 970 cm lr respectively, were just same wlth those obtainable with the original correspond-ing membrane which had not been treated with amine salt.
Then, these me~branes were dipped in a boiling water bath each for 30 minutes and used separately for the electrolytic treatment of NaCl under the same conditions as was disclosed in the ~oregoing Example l, and as the cation exchange membrane in each case.
Although the initial bath voltage showed a rèl~tively high value, however, it dr~pped to 3~2 volts after lapse~ of one day. The current efficiency amounted to 67% for the productlon of 20.3~ of NaOH.
An untreated membrane t'N-110" was dipped in a boi.ling water bath for 30 minutes and then used as the cation exchange membrane for tha same purpose under the same operating conditions to treat NaCl as ~efore, the current efficiency amounted to 58%
for producing 21.4~ - NaOH. This me~ns a considerably lower value. The bath voltage was 3 0 volts. From these results, the superior cation permeability of the amine salt-trea~ed membranes ; may be clearly seen.
After lapse of 48 hours of the electrolytic -treatment of the aqueous Na~ solution with use of the amine salt-treated membrane, the latter was washed with water and then dried up.
When observing the infra red spectrums, it was found that other-wise appearing absorptions caused by the presence of benzyl ra-.~ 30 dical and at 700 and 750 cm l, respectively, had complètely .; .
,': .,~ /1 ,. ,~, ,~_ 1 disappeared, showing those c~btail-able with untreated N-llO mem-branes.
It may be well suppoxed that during two day-electrolytic treatment period of NaCl that the arnine salt has been completely separated.
When observed with ultra violet spectrum, it was ob-served that the trimet~ylammonium chloride aqueous solution shown max ~ value at 260 ~.
When said N-llO membrane was dipped in a trimethylbenzyl ammonium chloride aqueous solution at 80C for about an hour and the amine salt aqueous solution was analyzed under UV-spectrum before and after the treatment, i-t was found that the a~line salt was consumed during the treatment in the specific ~uantlty of 0.~9 x 10 3 mol/g dry resin, and that the amine salt had reacted substantially in one-to-one reacting ratio with the ion-exchangeable radicals present in and on the membrane substxate.
~; From the foregoing, it may be well supposed that by the foregoing aMine salt treatment, an ion complex of (S03 )(N
is once formed which can be, however, easily separated off in the course of the electrolytic treatment of NaCl, Example 14 ~ hen the "NAFION N-llO"-rnembrane treated with trimethyl-benzyl ammonium chloride which was used in the foregoing Example 13, and then heat treated, is dipped in a boiling water bath for 30 minutes, it represents an aqueous swelling rate of about 11%. When this membrane is used for the electrolysis of NaCl under the operating conditions as set forth hereinbefore in Table 1 and at a 20% concentration of the NaOH pres~nt in the cathodic chambers the results will be:
Current efficiency .~ 69~;
Bath voltage....,....,. .~,~,..~..., ,..~.,.3.15 volts;
. ' ,.
a~
~z~
1 After lapse of three days, the membrane is taken out and the rate oE swelling thereo~ in a 20%-NaOH aqueous solution, amounts to abou-~ 14%
On the other hand, when a sheet of membrane "NAFION N-110"
is dipped in an aqueous NaOH-solution at 80C for an hour, the rate of swelling decreases with increased concentra-tion o~ the NaOH-solution. When these membranes are used for the electrolysis of NaCl under the operating conditions as set forth in the fore-going Table 1 and at a concentration of 20% of NaOH-solution present in the cathodic chamber, the current efficiency will vary with increase of the degree of swelling~ With the lower rate of swelling of the membrane treated beforehand with higher concen-tration of NaOH-solution, the current efficiency and the bath voltage will be higher.
After lapse of three days of electrol~tic tre~tment the membrane is taken out and subjected again to measurement of , the swelling degree in a 20%-NaOH-~queous solution, The swelling degree is found to have varied, as shown on the attached drawing.
When the membrane is treated with an aqueous solution O~ trimethyl benzyl ammonium chloride and then used for the desired electrolysis, the degree Q~ swelling being 14%, the treated membrane shows a current e~iciency of 69% and ~ bath voltage of 3.15 volts, while the corresponding caustic soda-treated membrane showing the similar`degree of swelling: 14%, shows à
current efficiency of 61%, respectively. Therefore, it will be seen that with same degree of swelling, the amine salt-treated membrane shows a rather favourahle effect. In this case, the quantity of ion exchange radicals: (-SO3Na)j can be deemed as subject to no change. When the respective concentration of Ma and OH present in the membrane substrate are expressed by CNa and COH , the ratio of COH / CNa will be same in the .:~ ` ' '` .
~ `
both. Now assuming the respective moving velocities of OH ~ions and Na ~ions are expres~ed by U~ and U~a , then the ratio betweerl the both will be:
, Ur OH / Na In that the product of the concentration of an ion in the membrane and the velocity of the ion in the membrane represents the current expended in passage of the ion through the membrane, current ef-ficienc~, Ceff~ representing the percentage of current supplied which contributes to the formation of NaOH may be defined as follows:
C = 100 x (CNa Na ; e~f - .
UNa ) ~ ~COH U~H
From the deining equations of Ur and Ce~ the following rela-tionship may be derived:
[ 100 1 r (COH / CN ~ , Ceff .-When Ur is calculated from this formula~ its valuefor the membranes treated with trime-th~lbenzyl ammonium chl~ride will be lower by about 30 in comparison with that of the membranes which have not been subjected to such salt treatment, The above difference may be attributed to the ~act that the membranes subjected to amine salt treatment as suggested herein represent generally a substantially improved current efficienc~ and with least possible increase of the bath ~ltage.
3~
.~
:', .
~.
Claims (5)
1. A cation exchange membrane for the electrolysis of alkali halide, having as its ion exchange radicals, sulfonic acid radicals, said membrane having been treated with primary, secondary or tertiary monoamine or its salt or quarternary ammonium salt and then heat-treated at a temperature higher than 100°C and lower than melting point of the reaction product and then subjected to drying.
2. A membrane of claim 1, characterized by the primary, secondary or tertiary monoamine salt or the quaternary ammonium salt being represented by an organic monoammonium salt structure as expressed by the following general formula:
(NR1R2R3R4X) where R1 stands. for alkyl; aryl; aralkyl or halogen derivative of any one thereof; R2, R3 or R4 stands for hydrogen;
alkyl, aralkyl or halogen derivative of any one thereof; and X
stands for F; C1; Br; I; OH; NO3; carboxylic radical; or any inorganic acid radical.
(NR1R2R3R4X) where R1 stands. for alkyl; aryl; aralkyl or halogen derivative of any one thereof; R2, R3 or R4 stands for hydrogen;
alkyl, aralkyl or halogen derivative of any one thereof; and X
stands for F; C1; Br; I; OH; NO3; carboxylic radical; or any inorganic acid radical.
3. A membrane of claim 1, characterized by the alkyl aryl or aralkyl being of C8 or fewer carbon atoms.
4. A membrane of claim 1, characterized by the membrane having been treated in the foregoing sense only on one side there-of.
5. A membrane of claim 1, characterized by the base material of the membrane being a fluorocarbon resin.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23355/1977 | 1977-03-04 | ||
| JP2335577A JPS53108098A (en) | 1977-03-04 | 1977-03-04 | Electrolytic method for alkali halide |
| JP110802/77 | 1977-09-14 | ||
| JP52110802A JPS608013B2 (en) | 1977-09-14 | 1977-09-14 | Improvement method of cation exchange membrane |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1120429A true CA1120429A (en) | 1982-03-23 |
Family
ID=26360704
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000298200A Expired CA1120429A (en) | 1977-03-04 | 1978-03-03 | Treatment of cation exchange membrane with monoamine its salt, or quaternary ammonium salt |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4246091A (en) |
| CA (1) | CA1120429A (en) |
| DE (1) | DE2810018A1 (en) |
| FR (1) | FR2382520A1 (en) |
| GB (1) | GB1549586A (en) |
| SE (1) | SE7802467L (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6041085B2 (en) * | 1978-05-30 | 1985-09-13 | 旭化成株式会社 | Melt processing method for fluoropolymer |
| US4376030A (en) * | 1979-08-27 | 1983-03-08 | The Dow Chemical Company | Electrolytic cell ion-exchange membranes |
| JPS5655577A (en) * | 1979-10-06 | 1981-05-16 | Toyo Soda Mfg Co Ltd | Electrolyzing method for alkali metal halide |
| US4381983A (en) * | 1980-06-02 | 1983-05-03 | Ppg Industries, Inc. | Solid polymer electrolyte cell |
| GB8331860D0 (en) * | 1983-11-29 | 1984-01-04 | Ici Plc | Exchange membrane |
| US5302269A (en) * | 1990-06-11 | 1994-04-12 | The Dow Chemical Company | Ion exchange membrane/electrode assembly having increased efficiency in proton exchange processes |
| JPH08501653A (en) * | 1990-06-11 | 1996-02-20 | ザ ダウ ケミカル カンパニー | Ion exchange membranes with increased efficiency in the proton exchange method. |
| US5747546A (en) * | 1996-12-31 | 1998-05-05 | The Dow Chemical Company | Ion-exchange polymers having an expanded microstructure |
| US6468657B1 (en) | 1998-12-04 | 2002-10-22 | The Regents Of The University Of California | Controllable ion-exchange membranes |
| GB0009506D0 (en) * | 2000-04-17 | 2000-06-07 | Innogy Ltd | Ion exchange membrane |
| WO2002096983A1 (en) * | 2001-05-31 | 2002-12-05 | Asahi Kasei Kabushiki Kaisha | Fluoropolymer ion-exchange membrane |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3562139A (en) * | 1968-08-05 | 1971-02-09 | Ionics | Cationic-anionic ion-exchange membrane |
| JPS5140556B2 (en) * | 1971-11-26 | 1976-11-04 | ||
| DE2354711B2 (en) | 1972-12-12 | 1975-08-14 | Asahi Kasei Kogyo K.K., Osaka (Japan) | Resin diaphragm and process for its manufacture |
| IL45141A (en) * | 1973-07-19 | 1977-02-28 | Cook E | Process and apparatus for electrolysis |
| US3884885A (en) * | 1973-08-01 | 1975-05-20 | Du Pont | Melt processing of fluorinated polymers |
| DE2437395C3 (en) * | 1973-10-15 | 1979-02-08 | E.I. Du Pont De Nemours And Co., Wilmington, Del. (V.St.A.) | Film made from fluorine-containing polymers with side chains containing sulfonyl groups |
| US3954579A (en) | 1973-11-01 | 1976-05-04 | Hooker Chemicals & Plastics Corporation | Electrolytic method for the simultaneous manufacture of concentrated and dilute aqueous hydroxide solutions |
| US3969285A (en) * | 1973-12-17 | 1976-07-13 | E. I. Du Pont De Nemours And Company | Heat-treated fluorocarbon sulfonylamine cation permselectivity |
| US4166014A (en) * | 1973-12-27 | 1979-08-28 | Tokuyama Soda Kabushiki Kaisha | Electrolytic diaphragms, and method of electrolysis using the same |
| US3884777A (en) * | 1974-01-02 | 1975-05-20 | Hooker Chemicals Plastics Corp | Electrolytic process for manufacturing chlorine dioxide, hydrogen peroxide, chlorine, alkali metal hydroxide and hydrogen |
| US3985631A (en) * | 1975-08-13 | 1976-10-12 | Diamond Shamrock Corporation | Pretreatment and start-up of electrolytic cell membranes |
-
1978
- 1978-03-03 GB GB8520/78A patent/GB1549586A/en not_active Expired
- 1978-03-03 CA CA000298200A patent/CA1120429A/en not_active Expired
- 1978-03-03 SE SE7802467A patent/SE7802467L/en unknown
- 1978-03-06 DE DE19782810018 patent/DE2810018A1/en not_active Ceased
- 1978-03-06 US US05/883,675 patent/US4246091A/en not_active Expired - Lifetime
- 1978-03-06 FR FR7806303A patent/FR2382520A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| US4246091A (en) | 1981-01-20 |
| GB1549586A (en) | 1979-08-08 |
| FR2382520A1 (en) | 1978-09-29 |
| DE2810018A1 (en) | 1978-09-21 |
| FR2382520B1 (en) | 1980-09-19 |
| SE7802467L (en) | 1978-09-05 |
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